Answer / Justification:
In Britain, sea wheatgrass is regarded as a primary dune colonizer, where it develops dense swards on pre-established foredunes. Both native and exotic plants grow in association with sea wheatgrass on incipient dunes and foredunes in Victoria. On the incipient dunes, such plants may include native hairy spinifex, and the exotics Cakile spp. (sea rockets) and Euphorbia paralias L. (sea spurge). On the foredunes, the vegetation is more varied and includes the native plants Atriplex cinerea Poiret X A. paludosa (coast saltbush), and Ficinia nodosa (Rottb.) Goetgh., Muasya & D.A. Simpson (knobby club rush), with Lepidosperma gladiatum Labill. (coast sword-sedge) growing in the swale in the lee of incipient dunes. On open sites on the foredunes, hardy succulents such as native and naturalized Carpobrotus spp. (pigface), and native plants Rhagodia baccata (Labill.) Moq. (seaberry saltbush) and Tetragonia tetragonioides (Pall.) Kuntze (sea spinach), manage the inhospitable environment remarkably well, as does the native Geranium solanderi var. solanderi Carolin (native geranium). Exotic weed species such as Fumaria spp. (fumitory), Oxalis spp. (soursob) and Allium triquetrum L. (angled onion) are just a few of the smaller flowering plants, also found in association with sea wheatgrass on the foredunes. Hilton et al. (2006) proposed that the sand-binding ability of sea wheatgrass makes it more resilient to erosive processes in comparison to native flora. Indeed, sea wheatgrass is one of four exotic species that were noted by Heyligers (1985) as being more efficient than native species at trapping sand and building dunes where otherwise dunes would not have formed. Such dunes have the potential to limit sediment movement, thereby changing the ecosystems and geomorphology of the coastlines on which they appear. Thus it is of concern that sea wheatgrass can rapidly colonize the swash and incipient dunes after propagules are washed ashore following storms. One example where sea wheatgrass has spread with great rapidity is along the Younghusband Peninsula in South Australia, where James (2012) reports that the plant has spread at approximately 18 ha per year, outcompeting native species and altering ecosystems (The Biology of Australian Weeds 63. Thinopyrum junceiforme (Á. Löve & D. Löve) Á. Löve). Native foredune species may be displaced by this species, with its dramatic spread. Develops monocultures in many areas, displacing others as the primary pioneer coloniser species, and may spread at a rate of 18+ hectares per year (Gaining new ground: Thinopyrum junceiforme, a model of success along the South Eastern Australian coastline).